1. Field of the Invention
The present invention relates to a liquid discharge recording head and an ink jet recording apparatus, in particular, to a sealing structure of an inner lead mounting part in the liquid discharge recording head.
2. Related Background Art
The recording apparatus of liquid discharge method such as an ink jet printer is a so-called recording apparatus of non-impact recording method that is capable of fast recording, and recording on various recording media, and that has a feature of barely producing noise during recording. Thus, the recording apparatus of liquid discharge method is widely adopted as a recording apparatus of a printer, a word processor, a facsimile, a copying machine and the like.
FIGS. 22A and 22B show the main parts of the liquid discharge recording head according to one conventional example, where 22A is a perspective view showing the discharging surface, and 22B is a perspective view of the opposite surface of FIG. 22A.
As shown in FIG. 22A, the recording head 1001 serving as a liquid discharge recording head is configured by a recording element 1100, a flexible wiring substrate 1300, a support member 1500 and the like. The recording element 1100 heats the ink with an electrothermal conversion body serving as a heating resistance element, and discharges the ink droplets through the action of film boiling. The flexible wiring substrate 1300 applies driving signal and the like from the device main body (not shown) to the recording element 1100. The support member 1500 forms an ink flow path for supplying ink from the ink tank (not shown) to the recording element 1100.
The support member 1500 connected to the ink tank includes a filter 1504 and a sealing rubber, 1505 at the connecting part, and forms a flow path for leading the ink from the ink tank to the recording element 1100, as shown in FIG. 22B.
As shown in an exploded perspective view of FIG. 23, the supply port (not shown) of the recording element 1100 is connected by an adhesive 1501 in correspondence to the ink supply port 1506 serving as an outlet of the flow path. The recording element 1100 is electrically connected to the flexible wiring substrate 1300 having an opening 1303 for incorporating the element. Specifically, the flexible wiring substrate 1300 is fixed to the support member 1500 with the adhesive 1501 so that the inner lead 1302 of the flexible wiring substrate 1300 is connected to the electrode part 1103 of the recording element 1100 adhered and fixed to the support member 1500. Further, the location having an external signal input terminal 1301 for inputting the drive signal and the like from the device main body with respect to the flexible wiring substrate 1300 is adhered and fixed to the side surface of the support member 1500 by the adhesive 1503.
FIGS. 24A and 24B are explanatory views showing the assembly steps of the recording head 1001. A nozzle plate 1102 with a plurality of discharge ports 1101 and an electrode part 1103 are provided on the main surface of the recording element 1100, and are incorporated in the opening 1303 of the flexible wiring substrate 1303. The inner lead 1302 is also arranged in the opening 1303. A gold, bump 1104 is formed on the electrode part 1103, and the inner lead 1302 and the electrode part 1103 are electrically connected through TAB (Tape Automated Bonding) mounting technique by way of the bump 1104 (refer to Japanese Patent Application Laid-Open No. Hei 10-000776).
As shown in FIG. 25A, the periphery of the side wall 1107 of the recording element 1100 is sealed with a first sealing agent 1201. Further, the electrically connecting portion by the inner lead 1302 is sealed with a second sealing agent 1202, so that the electrically connecting portion is protected from corrosion due to ink and external force (refer to Japanese Patent Application Laid-Open No. 2001-130001).
However, the above prior arts have disadvantages. That is, as shown in FIG. 25B, those of low viscosity is used for the first sealing agent 1201 to be filled to the periphery of the side surface of the recording element 1100 so as to be penetrated to the back surface of the electrically connecting portion that cannot be directly applied. The material having flexibility to be elastically deformed is used so that the sealing agent 1201 does not apply excess stress to the recording element 1100. The second sealing agent 1202 for sealing the front side of the electrically connecting portion must have high viscosity and rigidity against external force so as not to spread across the surface of the nozzle plate 1102 including a plurality of discharge ports 1101. Thus, the sealing agent having properties different from the first sealing agent 1201 must be used for the second sealing agent 1202, and the usage of two types of sealing agents increases the material cost.
In order to reliably seal the electrically connecting portion with the sealing agent 1202 having high viscosity and low fluidity, the sealing agent 1202 is overlapped by a distance L1 from the edge of the opening 1303, and must be applied at a height of about H1 on the base film 1307.
Recently, the size of the discharged liquid tends to be increasingly microscopic due to the demand of higher fineness of the image recording quality. If each ink discharged amount from the nozzle is made into a smaller liquid to a size of 1 pl (pico liter) or less, the image recording quality is easily influenced by air current or movement speed of the recording head. Thus, in order to have the recording liquid land at a suitable position, it is extremely important to have the distance (distance to papers) between the discharge port surface of the recording head and the recording medium (recording paper and the like) reduced as much as possible. In a recording apparatus, a spacing of about 2 mm is formed between the recording head 1001 and the recording medium such as recording paper so that they do not come in contact with each other. However, the higher the height of the sealing agent 1202 on the flexible wiring substrate 1300, the spacing between the nozzle plate 1102 and the recording medium must be made larger, which causes lowering of image recording quality. In other words, in the conventional configuration described above, the expanded second sealing agent is likely to contact the recording medium, which is one cause of inhibiting reduction of the distance to papers.
A technique for preventing the spread of sealing agent across the nozzle plate surface is disclosed in Japanese Patent Application Laid-Open No. Hei 8-048042, for example, but faces a challenge in that height H1 is also required in terms of sealing the base film of the flexible wiring substrate.